Conventional tracking cart systems are used in factories, warehouses, hospitals and libraries to transfer articles, and are equipped with a traveling rail laid on either a ceiling or a floor surface. FIG. 6 shows an example in which a travelling rail is laid on the ceiling of a clean room. 2 is a processing apparatus for processing, for example, semiconductors, etc. 4 is a grated floor surface and 6 is a ceiling. A traveling rail 8 is used to allow a traveling unit 10 to travel and a hoisting unit 12 elevates and lowers a hand 14 via a belt 16. When the hand 14 lowers, a chuck grips a work 20 on a loading station 18 and the hand 14 is then elevated to transfer the work 20.
In FIG. 6, the tracking cart system does not interfere with personnel working in the area unless the hand 14 is lowered and serves as an excellent transfer system that enables fast loading when the loading station 18 is located at height. If the loading station 18 is located, for example, as low as a person's waist, the hand 14 must travel some distance from the ceiling area, thereby increasing both loading times and the size of the hoisting unit 12.
FIG. 7 shows an example in which the traveling rail 22 is provided near the floor surface 4. In this example, a hand 26 provided on a tracking cart 24 is, for example, rotated to load the work 20. Under this configuration, only a small amount of time is required to load the work 20, but the track 22 blocks existing passages to obstruct person, handcarts and other forms of trackless unmanned transfer carts (hereafter, such carts are referred to as "unmanned transfer carts"). In a typical layout for a tracking cart system, a main passage branches into a loop-like passage with processing apparatuses located on the respective sides of the loop-like passage. In such a layout, a traveling rail is conveniently arranged along the loop-like passage and is connected to a traveling rail on the main passage. In the system in FIG. 7, when the traveling rail 22 is arranged in a loop-like form, person, handcarts and unmanned transfer carts cannot enter the area encompassed by the traveling rail 22. If a switchback is used instead of a loop, only one tracking cart can enter this area at a time, thereby reducing the system's transfer capability.
The present invention is intended to provide an unmanned tracking system that enables a loop to be constructed without hindering person, handcarts and unmanned transfer carts from approaching the loading station.
It is an additional objective of the present invention is to enable fast loading using a simple configuration.
It is an additional objective of the present invention to prevent any degradation in the cleanliness level of a clean room.
It is an additional object of the present invention to prevent collisions between the carts in the system and obstacles such as person.
According to the present invention, a tracking cart travels in such a way as to be suspended from a travelling rail laid above a floor surface, for example, above head height, preferably at 1.7 to 2 m from the floor surface so as to form a clearance beneath the cart sufficient to allow person and handcart etc. to approach a loading station. A loading means for loading a work by moving within a near-horizontal plane is provided under the tracking cart. In the loading means, a fork preferably moves forward and backward nearly perpendicularly to the travelling rail and may be rotationally moved by an arm.
Preferably, the loading means comprises a fork elevating section that moves forward and backward nearly perpendicularly to the travelling rail and a fork mounted on the fork elevating section.
In addition, it is preferable that the tracking cart is provided with a clean fan unit for sucking dust from the loading means.
More preferably, the system has a means for detecting an obstacle under said traveling rail to prohibit the approach of the tracking cart when an obstacle is detected.